"Over the last couple of weeks, Mozilla has finally stepped up its 64-bit testing process. There are now five slaves dedicated to building Firefox for Windows x64, which means that from Firefox 8 and onwards, you'll be able to pick up 64-bit builds that are functionally identical to its 32-bit cousins but operating in native 64-bit CPU and memory space." Th 64bit version is about 10% faster, benchmarks show.

One thing you failed to mention is that in general there has been a bit of crossover on both the CISC and RISC sides.... X86 and X86_64 have both moved a little bit towards the RISC side and vice versa (PPC anyway). The bottom line is when you look at the ARM processors or the Intel/AMD processors ....... they all have good preformers and poor preformers.